DNA methylation in invertebrates seems to play a different role as in mammals and its evolutionary conservation among invertebrates is unclear. Only two studies describe crustacean methylomes giving just a small overview. The parthenogenetic reproducing marbled crayfish display a high environmental adaptability besides its genetic uniformity and thus, possess the necessary attributes of a laboratory model organism. The aim of this work was to characterize the methylome of the marbled crayfish at single-base resolution using whole-genome bisulfite sequencing in an attempt to give new insights into DNA methylation in crustaceans and thus, in the evolutionary conservation among invertebrates. Analysis of the mitochondrial DNA of different marbled crayfish strains revealed a single origin and suggests to consider the marbled crayfish as independent asexual species Procambarus virginalis. Furthermore, since the P. virginalis possess a large genome size, the transcriptome was assembled and comparison to other species revealed a relative good quality of the first draft transcriptome as well as the presence of a conserved DNA methylation system in P. virginalis. Analysis of the CpG depletion in protein-coding sequences and mass spectrometry confirmed historical germline and current DNA methylation in various tissues of P. virginalis. The methylome was characterized by the key features of animal methylomes with methylation targeted to gene bodies. The gene bodies displayed the typical pattern of a mosaically methylated invertebrate genome and a bimodal distribution of their methylation levels. Targeted gene bodies were annotated as housekeeping genes and methylation showed a parabolic relationship to housekeeping gene expression suggesting that the DNA methylation of housekeeping genes might fine-tune their expression. Additionally, repeats were generally hypomethylated and the methylation of repeats depended on their position to gene bodies. Finally, inter-individual and inter-tissue comparison of gene body methylation revealed a high reproducibility of the methylation patterns, while inter-species comparison between P. fallax and P. virginalis displayed an overall hypomethylation in the P. virginalis genes which however, could not explain the by mass spectrometry detected global hypomethylation in P. virginalis. These findings uncovered that the P. virginalis methylome is characterized by tissue-invariant housekeeping gene methylation. This thesis describes novel insights into the evolutionary conservation of gene body and repeat methylation in invertebrates, especially crustaceans, and the preferential methylation of housekeeping genes highlights a functional difference to the tissue-specific methylation in mammals.

The marbled crayfish (Procambarus fallax f. virginalis) has become one of the potentially most dangerous nonindigenous crayfish species spreading in European countries and elsewhere. This taxon reproduces parthenogenetically and recently has been verified as a vector of the crayfish plague pathogen. Here, we report on two established populations of marbled crayfish in the Czech Republic. The marbled crayfish was observed during autumn 2015 in an urban pond connected by sewer piping with the Rokytka brook near its mouth to the Vltava River in Prague. Subsequently, three adult females, two of them having well-developed glair glands and oocytes, were captured in this pond during spring 2016, suggesting successful overwintering of the local population. Furthermore, four adult females were captured in an artificial pond at the Radovesická lignite spoil heap in the vicinity to the industrial conurbation of Bílina in summer 2016; one of them carried eggs. We tested these for the presence of the crayfish plague pathogen Aphanomyces astaci, with negative results. The introduction pathway for both populations is most likely a release from private aquaria, as these sites are popular for recreation activities. Our findings substantiate previous predictions that conurbations are likely to be the primary areas for marbled crayfish introductions.

10 January 2017

The Crustacean Society (TCS) has multiple scholarships and travel grants for its members.

Scholarships in graduate studies

The Crustacean Society annually awards up to six US$1000 scholarships in graduate studies on crustaceans in any of the following fields:

Biology of large branchiopods (Denton Belk Memorial Scholarship)

Physiology and reproductive biology

Ecology and behavioural ecology, population genetics, and behavior

Eystematics, biogeography, and evolution

Larvae and development

Anatomy or paleobiology

Applicants and their faculty sponsor must be a member of The Crustacean Society and be enrolled in an undergraduate or graduate degree program.
Student travel awards

The Crustacean Society awards up to ten US$450 awards to support student attendance at Crustacean Society meetings (Society for Integrative and Comparative Biology, mid-year society meeting, or the International Crustacean Congress). Applicants and their faculty sponsor must be a member of The Crustacean Society, be enrolled in an undergraduate or graduate degree program, be the presenter of an oral or poster presentation at the Crustacean Society meeting they attend and demonstrate financial need for society support of travel to the meeting.

Early-career, post-Ph.D. travel awards

The
Crustacean Society will award up to three US$1500 travel grants for
early-career researchers with a Ph.D. awarded within 5 years of the
application deadline. Extension of up to 8 years post-Ph.D. will be
considered at the discretion of the Program Officer for applicants
having taken a career break for family reasons. The grants shall cover
travel to present results of their research in any field of study
involving crustaceans at a Crustacean Society meeting (Society for Integrative and Comparative Biology,
mid-year society meeting, or the International Crustacean Congress).
The applicant must be a current member of The Crustacean Society at the
time of application.The closing date for all awards is 31 March 2017. Contact Dr. Joanne Taylor (jtaylor@museum.vic.gov.au) for more information. She is traveling until about Jan. 20, 2017; in the meantime, contact Mary Belk for forms (tcs1921@hotmail.com).

After interest in keeping crayfish (Crustacea, Decapoda, Astacida) in home aquaria peaked in the mid-2000s, the aquarium trade has become a novel introduction pathway for non-native crayfish species in Germany. Here, we provide an update on the ornamental crayfish trade approximately one decade after the ‘crayfish hype’ to explore the long-term implications in terms of bio-invasion risk. Specifically, species’ availability in e-commerce and potential invasiveness were assessed and compared to previous studies. Morphological and ecological traits of the offered species were compiled and related to their long-term availability (covering 2005–2015). In July 2015, a total of 31 online shops offered 28 crayfish species, which represents a decline of 24% in species diversity compared to the late 2000s. The estimated rate of import of new species has considerably flattened and approaches pre-hype values (<1 species year−1). However, the risk associated with the offered species, as assessed by a risk screening tool, has not decreased compared to the late 2000s. Long-term availability in the trade was primarily determined by bright coloration, the ability to reproduce under warm aquarium conditions, and a preference for lentic habitats. Species featuring such traits are likely to persist in the aquarium trade and include four high-risk species, most notably invasive and crayfish plague-carrying red swamp crayfish (Procambarus clarkii) and Marmorkrebs (Procambarus fallax f. virginalis). Persistent propagule pressure from aquaria has substantially contributed to the establishment of both species in Germany, stressing the need for more effective pathway management.